Synthetic absorbable biocompatible polymers are well known in the art. Such polymers are typically used to manufacture medical devices, which are implanted in body tissue and absorb over time. Synthetic absorbable biocompatible polymers include homopolymers, copolymers (random, block, segmented and graft) of monomers such as glycolic acid, glycolide (d, l, meso and mixtures thereof), lactic acid, lactide, .epsilon.-caprolactone, trimethylene carbonate and p-dioxanone. Numerous U.S. Patents describe these polymers including U.S. Pat. Nos. 5,431,679; 5,403,347; 5,314,989; 5,431,679; 5,403,347; and 5,502,159.
Block copolymers of glycolide, para-dioxanone and caprolactone have been described in the prior art. U.S. Pat. No. 5,080,665 describes deformable surgical clips or staples manufactured from block copolymers and graft copolymers having at least 50 to about 90 mole percent hard phase repeating units and the remainder being soft phase repeating units. The hard phase repeating units of the copolymer consisting of glycolic acid ester, lactic acid ester linkages and mixtures thereof. The soft phase repeating units comprising 1,3-dioxan-2-one (trimethylene carbonate), 1,4-dioxan-2-one (para-dioxanone) or .epsilon.-caprolactone linkages. These polymers are described as having a Young's modulus over 200,000, as well as a flexural strain at break of greater than about 3 percent.
Similarly, block copolymers of glycolide or lactide blocks attached to blocks containing para-dioxanone and glycolide or lactide have been described in U.S. Pat. No. 5,314,989.
Unfortunately, neither of these patents recognize that especially flexible sutures could be manufactured from a copolymer of glycolic repeating units copolymerized with a random prepolymer predominately of para-dioxanone and .epsilon.-caprolactone repeating units.
Accordingly, what is needed in this art are novel polymer compositions which have high tensile strength but low modulus, useful as, for example, sutures in plastic surgical indications.